In the China wire and cable products, there is no very small structure with a concentric cable. Some developed countries abroad are committed to research in this area and put it into practice. In the British Standard, BS4553-92 copper core PE insulated cable for power supply, the same core layer can be used as The sexual conductor and the grounding conductor are made of unplated annealed copper wire in accordance with BS4109.If the number, diameter and resistivity of the copper wires in each specification cable are the same as the core layer, the right winding should be adopted.
So what does concentric neutral mean?
The Concentric Neutral is the current flowing from one end to the other, then into the ground and back into the wire at the starting position.
The wrapping pitch and the number of threads should make the minimum coverage rate reach 90%, and the wrapping tape that does not absorb moisture should be overlapped immediately outside the same core layer. The NYCY type in the German standard DIN57271-83 adopts the same core layer conductor and can be used as a neutral wire, a ground wire or a neutral wire, and it can be used as a shield wire at the same time. The number, diameter and resistivity of unplated annealed copper wires are also specified. Compared with the same type of cable, it has a compact structure and a round shape, which can save about 10% of the sheath cable material. Therefore, according to the above structure.
The characteristics, cross-sectional area requirements, equipment and production technology used to formulate the structural design principles of low power cable concentric conductors.
- In order to facilitate production and management, the wire diameter of the same core conductor should be unified as much as possible.
- According to the production equipment, the minimum wire diameter shall be specified under the condition that it is evenly distributed on the stranded insulating core around the cladding and the spacing is not greater than 4mm. The number of concentric conductors is as small as possible.
- In order to ensure the uniformity of the same-core conductors without relative sliding, and to ensure that the
The cable appearance is round. Using layered non-woven fabric or PVC wrapping method, that is, insulating core into cable wrapping tape + concentric conductor twisted spiral copper tape wrapping + non-woven fabric tape overlapping wrapping.
- There are three types of structures. The structure of three-phase four-wire cable is a structure, and the structure of three-phase five-wire cable is b and c.
In the structure, the concentric conductor is wrapped outside the cable core. It can be N wire (neutral wire), PE wire (protective earth), or PEN (neutral wire and protective earth shared), and the material is copper Wire or copper tape, or copper wire plus copper tape. The carrying surface is the same or half of the electric phase core
- In the structure, the N wire is in the cable core, and the neutral wire is wrapped around the cable core as a PE wire. The neutral wire can be copper wire or copper wire plus copper tape. The cross section is half of the cable phase core
- In the structure, the N wire is wrapped outside the copper core, and the PE wire composed of copper wire is wrapped outside the N wire, and the copper wire is composed of copper tape to form a double-layer shielding structure. The cross-section is the same as the phase core of the cable.
Advantages of the same-core conductor and shielded neutral power cable
- When transmitting power, it will not cause interference to surrounding electrical equipment; it also eliminates the influence of external electromagnetic interference on electrical equipment connected to this cable
- It can avoid breakdown or damage caused by strong lightning electromagnetic effect voltage, and improve the lightning protection effect and reliability of high-rise buildings
- It can improve the sensitivity of the overcurrent protection device at the head end of the line, so that the cable and the electrical equipment connected to it can be effectively protected
- It has low and uniform forward (reverse) sequence and zero sequence impedance, which is conducive to improving the quality of copper electricity
- TN-C and TN-C-S system power supply suitable for coreless cables
- It can eliminate the ground fault caused by the insulation breakdown of one phase as soon as possible
- Convenient processing, high flexibility and easy construction
- Can reduce costs